1. Technical Field
The present invention relates to a printing apparatus including an image process portion.
2. Related Art
Existing printing apparatuses include a printing head that includes a plurality of nozzles formed therein through which inks are ejected onto a printed medium such as paper; and a control apparatus that performs printing processing for printing images on the printed medium by driving the printing head. For the purpose of high-quality image printing, blocks of image data of high resolution are sequentially transmitted to the control apparatus from an external apparatus. Every time the control apparatus receives such a block of image data, the control apparatus stores the block of image data into a buffer unit, and concurrently therewith, the control apparatus performs the printing processing on the basis of blocks of image data having been stored in the buffer unit. In such an existing printing apparatus, however, when a data volume of each block of image data is large, it takes a long time until the completion of transmission of each block of image data, thereby causing a situation in which a waiting time for waiting for a subsequent completion of transmission of a block of image data occurs and this occurrence of waiting time brings printing operation into a waiting state. Further, during this waiting state, a previously printed portion on the printed medium becomes dry, thereby resulting in a situation in which drying unevenness occurs.
With respect to such a problem, there is proposed a printing apparatus in which an image process portion that performs color conversion processing and halftone processing is provided for the purpose of shortening a period of time required to complete transmission of image data from an external apparatus to the printing apparatus. This image process portion included in such a printing apparatus repeatedly executes the color conversion processing and the halftone processing in this order on image data corresponding to several rasters and received from the external apparatus, until all rasters of image data are processed. In the case where, however, the processing capacity of the image process portion is low, a period of time required for the color conversion processing and the halftone processing on image data becomes long, thereby still causing a situation in which a waiting time occurs. Thus, there is still room for improvement in reduction of the situations in which the drying unevenness occurs.
Thus, there is proposed a printing apparatus configured to, in the case where it takes a long time for such an image process portion to complete its processing on each block of image data, reduce the situations in which the drying unevenness occurs by shortening a period when printing operation is in such a waiting state, through a method of narrowing the sub-scanning direction size of each region existing on the printed medium and being subjected to printing through a corresponding movement (pass) of the printing head in a main-scanning direction (refer to, for example, JP-A-2012-11616).
This method, however, of narrowing the sub-scanning direction size of each region existing on the printed medium and being subjected to printing through a corresponding pass of the printing head results in increase of the number of passes of the printing head which are required to complete printing of all images onto the printed medium. As a result, a period of time required to complete printing onto the printed medium becomes long.